Are you talking about a Moen roman tub faucet?
If so, I believe they come from the factory with the short pieces of copper already installed in the sides and bottom of the valves. So the installer is to assemble them with a tee and short copper tube for the tub spout. Since this requires the installer to make sweat connections within 3"-5" of the factory connections I would imagine these factory connections are brazed or at least use a joining material that has a higher melting point than that of your standard solder. If you haven't ruined the joint, then I would just use sweat fittings to extend the nipples as you want them.
Some of these faucets come completely assembled on 10" centers.